title: Aqueous solutions of ionic liquids: study of the solution/vapor interface using molecular dynamics simulations.
abstract: We performed a detailed molecular dynamics study of the interfacial structure of aqueous solutions of 1-butyl-3-methylimidazolium tetrafluoroborate in order to explain the anomalous dependence of the surface tension on concentration. At low concentrations the surface tension decreases with concentration. At higher concentrations the surface becomes saturated; a plateau is observed in simulations with a non-polarizable force field while a possible increase is detected in simulations with a polarizable force field. The structure is characterized by a surplus of cations at the surface (with hydrophobic butyl chains pointing toward vacuum) which at low concentrations is only partly compensated by the anions because of asymmetric solvation. A more hydrophobic 1-butyl-3-methylimidazolium hexafluorophosphate is also simulated for comparison.
authors.affiliation: Department of Physical Chemistry, Institute of Chemical Technology, Prague, Technická 5, Praha 6, Czech Republic. jiri.kolafa@vscht.cz
authors.forename: Jan
authors.initials: J
authors.lastname: Picálek
authors.forename: Babak
authors.initials: B
authors.lastname: Minofar
authors.forename: Jirí
authors.initials: J
authors.lastname: Kolafa
authors.forename: Pavel
authors.initials: P
authors.lastname: Jungwirth
mesh_terms: D001881:Borates / Q000737:chemistry*; D003198:Computer Simulation; D007093:Imidazoles / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D008956:Models, Chemical; D012996:Solutions / Q000737:chemistry; D013500:Surface Tension; D014835:Volatilization; D014867:Water / Q000737:chemistry
chemical_list: C419324:1-butyl-3-methylimidazolium tetrafluoroborate; D001881:Borates; D007093:Imidazoles; D052578:Ionic Liquids; D012996:Solutions; D014867:Water